Method of producing hot-formed copper-base products



April 25, 1967 D. B. COFER Filed Oct. 20, 1965 2 Sheets-Sheet 1 Vi Z M ia GQQQQOGOOG GQUQUOOQQQQQ INVENTOR. Daniel B Co/r dur i i g BY:

A TTORNEYS D. B. COFER April 25, 1967 METHOD OF PRODUCING HOT-FORMEDCOPPER-BASE PRODUCTS 2 Sheets-Sheet 2 Filed Oct.

Q2121?! B Cofer ATTORNEYS BY: 1 m 1" United States Patent 3,315,349METHOD OF PRODUCING HOT-FORMED COPPER-BASE PRODUCTS Daniel B. Cofer,Carrollton, Ga., assignor to Southwire Company, Carrollton, Ga., acorporation of Georgia Filed Oct. 20, 1965, Ser. No. 498,774 9 Claims.(Cl. 29-528) This invention relates generally to the production ofcopper-base products and, more particularly to a method of producinghot-formed copper-base products from molten metal.

In the production of hot-formed copper-base products such as productshot-formed of pure or commercially pure copper or various copper alloys,it is generally desirable that the products exhibit a grain structurecharacterized by fine equi-axed grains having a minimum of grainalignment. This is because copper-base products having a grain structurewith these characteristics have the best tensile strength, ductility,electrical and thermal conductivity, and other properties for thecommercial use of the product.

It is to the production of hot-formed copper-base products having fineequi-axed grains with no grain alignment that the invention disclosedherein is admirably suited. This is because the invention provideshot-formed copper-base products having a grain structure characterizedby equi-axed grains of uniformly finer grain size and with less grainalignment than has been previously attainable in the prior art.

This grain structure is obtained by solidifying molten metal to obtaincast metal and by hot-forming the cast metal in substantially thecondition in which it solidified and in a manner which impartssubstantial movement to the cast metal along a plurality of angularlydisposed axes of deformation. Since the cast metal solidified frommolten metal at a temperature above its hot-forming temperature, thehot-forming of the cast metal in substantially the condition in which itsolidified permits the heating of the cast metal prior to hot-forming tobe completely eliminated or to be used simply to adjust the hot-formingtemperature of the cast metal immediately prior to hot-forming.

It is by its unique combination of solidifying molten metal to obtaincast metal and of hot-forming the cast metal in a particular conditionand in a particular manner that the invention disclosed herein provideshot-formed copper-base products having uniformly distributed equiaxedgrains of finer grain size and with less grain alignment than has beenpreviously attainable in the prior art. These and other features andadvantages of the invention will be more clearly understood from thefollowing description and the accompanying drawings in which likecharacters of reference designate corresponding parts throughout and inwhich:

FIG. 1 schematically shows one example of apparatus .suitable topractice the invention, this apparatus comprising a casting machine anda rolling mill having a plurality of roll stands;

FIG. 2 shows the transverse cross-sectional shapes of cast metal as itis hot-formed in a manner in accordance with the invention;

FIG. 3 shows the transverse cross-sectional shapes of cast metal as itis hot-formed in a manner not in accordance with the invention;

FIG. 4 is a photomicrograph of a portion of a transverse cross-sectionalsurface of a cast copper bar solidified in a continuous casting meanssuch as the casting machine shown in FIG. 1 and cooled by quenching tocold forming temperature;

FIG. 5 is a photomicrograph of a portion of a trans- ICC versecross-sectional surface of a copper rod produced by the invention;

FIG. 6 is a photomicrograph of a portion of a transverse cross-sectionalsurface of a copper rod produced by solidifying molten metal in acontinuous casting means such as the casting machine shown in FIG. 1 toobtain cast metal and hot-forming the cast metal in substantially thecondition in which it solidified and in a manner generally representedby the transverse cross-sectional shapes of FIG. 3 and using a number ofdeformations equal to the number used in the hot-forming of the copperrod of FIG. 5;

FIG. 7 is a photomicrograph of a portion of a transversecross-secti-onal surface of the copper rod of FIG. 6 after fouradditional deformations during hot-forming.

These figures and the following detailed description disclose a specificembodiment of the invention. However, it will be understood that thepresent invention is not limited to the details disclosed herein sinceit may be embodied in other equivalent forms without departing from theinventive concept.

The method of producing hot-formed copper-base products disclosed hereinis best understood in terms of means suitable to its practice such asthe apparatus schematically shown in FIG. 1 and which comprises acontinuous casting machine 10 and a rolling mill 11. The continuouscasting machine 10 serves as a means for solidifying molten metal 9 toprovide a cast bar 12 that is conveyed in substantially the condition inwhich it solidified from the continuous casting machine 10 to therolling mill 11 which serves as a means for rot-forming the cast bar 12into rod 16 or another hot-formed product in a manner which impartssubstantial movement to the cast bar 12 along a plurality of angularlydisposed axes.

The continuous casting machine 10 is of conventional casting wheel typehaving a casting wheel 13 with a casting groove (not shown) partiallyclosed by an endless belt 14 supported by the casting wheel 13 and anidler pulley 15. The casting wheel 13 and the endless belt 14 cooperateto provide a mold (not shown) into one end of which molten metal 9 ispoured to solidify and from the other end of which the cast bar 12 isemitted in substantially that condition in which it solidified.

The rolling mill 11 is of conventional type having a plurality of rollstands 17 arranged to hot-form the cast bar 12 by a series ofdeformations. The continuous casting machine 10 and the rolling mill 11are positioned relative to each other so that the cast bar 12 enters therolling mill 11 substantially immediately after solidification and insubstantially that condition in which it solidified. In this condition,the cast bar 12 is at a hot-forming temperature within the range oftemperatures for hotforming the cast bar 12 at the initiation ofhot-forming without heating between the casting machine 10 and therolling mill 11. In the event that it is desired to closely control thehot-forming temperature of the cast bar 12 within the conventional rangeof hot-forming temperatures, means for adjusting the temperature of thecast bar 12 (not shown) may be placed between the continuous castingmachine 10 and the rolling mill 11 without departing from the inventiveconcept disclosed herein.

It will be understood that with the apparatus of FIG. 1, the cast metalmay be of any one of a plurality of lengths determined by the lengths oftime the molten metal is solidified and may extend between thecontinuous casting machine 10 and the rolling mill 11. Thus, the stepsof solidifying molten metal to obtain cast metal and of hot-forming thecast metal are performed simultaneously. However, the apparatus of FIG.1 is shown only schematically because each'component of the apparatus isknown to those skilled in the art and because once the invention isunderstood, it will be apparent to Patented Apr. 25, 1967 -fied frommolten metal.

those skilled in the art that a direct chill casting machine or any oneof many other known devices may be substituted for the continuouscasting machine 10 shown in FIG. 1 and that a continuous forging machineor any one of many other known devices may be substituted for therolling mill 11 shown in FIG. 1. This is because the invention requiresonly means for solidifying molten metal to provide cast metal and meansfor hot-forming the cast metal in the condition and in the mannerdisclosed herein.

The manner in which the means for hot-forming cast metal must hot-formthe cast metal is best illustrated by reference to FIG. 2. From FIG. 2,it will be seen that as cast metal, such as the cast bar 12, iselongated into a hot-formed product such as rod 16, the cast metal has aplurality of transverse cross-sectional shapes which are alternatelysubstantially flattened and substantially round.

Roll stands 17 of a rolling mill 11 having roll passes (not shown) whichhot-form cast metal in a manner which results in these transversecross-sectional shapes are well known to those skilled in the art andthose skilled in the art will understand that this manner of hot-formingcast metal results in substantial movement of the cast metal not onlyalong an axis of elongation but also along axes angularly disposed tothe axis of elongation. It will also be understood that the hot-formingof a cast metal in a manner which imparts substantial movement to thecast metal along a plurality of angularly disposed axes may beaccomplished by techniques of hot-forming other than that represented bythe transverse cross-sectional shapes of FIG. 2.

Regardless of the technique of hot-forming used to obtain substantialmovement of the cast metal along a plurality of anugularly disposedaxes, the cast metal must enter the hot-forming means such as a rollingmill 11 while still in substantially that condition in which it solidi-That is, the cast metal must be substantially in its cast condition andnot be cooled to cold working temperature and reheated or homogenizedbetween its solidification from molten metal and the initiation ofhot-forming. However, it has been found that varying that temperature ofthe cast metal which results from the cast metal being delivered to themeans for hot-forming in substantially that condition in which itsolidified in order to maintain a particular hot-forming temperaturedoes not adversely affect the grain structure of copper rod produced bythe invention. It is for this reason that means (not shown) foradjusting the temperature of the cast bar 12 may be placed between thecontinuous casting machine 10 and the rolling mill 11 and that suchtemperature adjustments are consistent with the requirement of theinvention that the cast metal be in substantially that condition inwhich it solidified from molten metal.

The copper rod 19 of FIG. is representative of the hot-formedcopper-base products produced by the invention. This copper rod 19 wasproduced by solidifying molten copper-base metal in the continuouscasting machine of FIG. 1 to obtain cast metal and.- by hotforming thecast metal in a rolling mill 11 by a series of deformations representedby the transverse cross-sectional shapes of FIG. 2 and in substantiallythat condition in which it solidified. More specifically, the copper rod19 was produced by removing a cast bar 12 from the continuous castingmachine 10 while its temperature was still in the range of temperaturesat which copper is hot-formed and by initiating the hot-forming of thecast bar 12 while its temperature was still in this range and withoutheating between the casting machine 10 and rolling mill 11.

The copper rod 20 of FIG. 7 was produced by solidifying molten metal inthe continuous casting machine 10- of FIG. 1 to obtain cast metal and byhot-forming the cast metal in a rolling mill 11 by a series ofdeformations represented by the transverse cross-sectioal shapes of FIG.3 and in substantially that condition in which it solidified. The copperrod 20' of FIG. 6 is identical to the copper rod 20 except that thecopper rod 20' was deformed four fewer times in hot working than thecopper rod 20 and the same number of times as the copper rod 19.

Those skilled in the art will understand that the hotforming of castmetal by the series of deformations represented by the transversecross-sectional shapes of FIG. 3 does not result in substantial movementof the cast metal along a plurality of angularly disposed axes. Rather,substantial movement of the cast metal is only along the axis ofelongation of the cast metal as it is hot-formed. Thus, it will beunderstood that both the copper rod 20 and the copper rod 20' differfrom the copper rod 19 produced by the invention in that they have notbeen hotformed'in a manner which imparts substantial movement to thecast metal along a plurality of angularly disposed axes.

The copper rods 19, 20, and 20 were all produced with tough pitch copperand it will now be understood that the copper rod 19, the copper rod 20,and the copper rod 20' were all produced by solidifying molten metal inthe continuous casting machine 10 shown in FIG. 1 to obtain cast metalwhich was hot-formed in substantially that condition in which itsolidified. However, only the copper rod 19 was produced by solidifyingmolten copper-base metal in the continuous casting machine 10 shown inFIG. 1 to obtain cast metal and by hot-forming the cast metal insubstantially that condition in which it solidified and in a mannerrepresented by the transverse cross-sectional shapes of FIG. 2. That thecopper rod 19 produced by the invention has a grain structure superiorto that obtained by the methods represented by copper rods 20, and 20'is shown when FIGS. 5-7 are examined. When these figures are examined,it will be seen that FIGS. 57 are photomicrographs. The photomicrographsof FIGS. 5-7, as well as the photomicrograph of FIG. 4, were made at amagnification of X by slicing a transverse section from the particularcopper rod shown and by mounting, polishing, etching and placing thetransverse cross-sectional surface obtained in a metallograph inconventional manner.

When the photomicrograph of FIG. 5 is compared with the photomicrographsof FIGS. 6 and 7, it is readily apparent that both the copper rod 20 andthe copper rod 20 have grains 30 of larger size and with more grainalignment as at 31 than the copper rod 19. Thus, it is clear from FIGS.5-7 that the hot-forming of cast metal in a manner which impartssubstantial motion to the cast metal along a plurality of angularlydisposed axes provides copper rod 19 having a grain structure superiorto the grain structure of copper rods 20 or 20 which were produced bysolidifying molten metal to obtain cast metal and by hot-forming thecast metal in substantially that condition in which it solidified, butin a' manner which did not impart substantial movement to the cast metalalong a plurality of angularly disposed axes. In this connection, itshould be noted that the invention achieves this superior grainstructure with fewer deformations than were used in hot-forming thecopper rod 20 even though the as cast grain structure of the cast metalfor both the copper rod 19 and the copper rod 20 was substantially asshown in FIG. 4 prior to hot-forming.

It will now be evident that the failure to hot-form the copper rod 20and the copper rod 20' in a manner which imparted substantial movementto the cast metal along a plurality of angularly disposed axes causedboth the cop- .per rod 20 and the copper rod 20 to have poorer grainstructures than the copper rod 19. Thus, it is clear that the productionof hot-formed copper-base products having a superior grain structurerequires the solidifying of molten metal to obtain cast metal and thehot-forming of the cast metal in substantially that condition in whichit solidified and in a manner which imparts substantial movement to thecast metal along a plurality of angularly disposed axes.

It will be understood by those skilled in the art that many variationsmay be made in the embodiment chosen herein for the purpose ofillustrating the present invention without departing from the scopethereof as defined by the appended claims.

What is claimed as the invention is:

1. A method of producing a hot-formed copper-base product having a grainstructure characterized by uniformly distributed fine grains withsubstantially no grain alignment, said method comprising the steps ofsolidifying a molten copper-base metal to obtain cast metal and ofhot-forming said cast metal while said cast metal is in substantiallythat condition in which it solidified by deforming said cast metal asubstantial number of times to cause said cast metal to assume aplurality of successive alternately difierent cross-sections whichinclude several substantially flattened and elongated cross-sections andseveral substantially round cross-sections so as to impart substantialmovement to said cast metal along a plurality of angularly disposedaxes, said hot-forming serving to hot-form said product and to provide agrain structure characterized by uniformly distributed fine grains Withsubstantially no grain alignment.

2. The method of claim 1 where said method includes the step ofmaintaining the temperature of said cast metal within a range oftemperatures for hot-forming said cast metal between the solidificationof said cast metal from said moltefi' copper-base metal and theinitiation of hotforming.

3. The method of claim 2 wherein said method includes the step ofvarying the said temperature of the said cast metal within said range oftemperatures to obtain a particular temperature of said cast metal uponinitiation of hot-forming.

4. The method of claim 1 wherein one of said axes is an axis ofelongation of said cast metal and another said axes is an axistransverse to said axis of elongation.

5. The method of claim 1 wherein said method includes conveying saidcast metal to a means for hot-forming substantially immediately afterthe solidification of said cast metal from said molten copper-basemetal.

6. The method of claim 1 wherein said molten copperbase metal is toughpitch copper.

7. The method of claim 1 wherein the steps of solidifying said moltencopper-base metal to obtain cast metal and of hot-forming are performednearly simultaneously.

8. The method of claim 1 wherein said method includes extending the saidcast metal between a means for solidifying said molten copper-base metaland a means for hotforming.

9. The method of claim 1 wherein the step of solidifying the said moltencopper-base metal provides cast metal in a plurality of lengths witheach length being determined by the amount of said molten copper-basemetal solidified.

References Cited by the Examiner UNITED STATES PATENTS 2,019,496 11/1935Kohlhaas. 3,209,452 10/1965 Schneckenburger 2952 8 FOREIGN PATENTS4/1937 Great Britain.

OTHER REFERENCES JOHN, F. CAMPBELL, Primary Examiner. R. F. DROPKIN,Assistant Examiner.

1. A METHOD OF PRODUCING A HOT-FORMED COPPER-BASE PRODUCT HAVING A GRAINSTRUCTURE CHARACTERIZED BY UNIFORMLY DISTRIBUTED FINE GRAINS WITHSUBSTANTIALLY NO GRAIN ALIGNMENT, SAID METHOD COMPRISING THE STEPS OFSOLIDIFYING A MOLTEN COPPER-BASE METAL TO OBTAIN CAST METAL AND OFHOT-FORMING SAID CAST METAL WHILE SAID CAST METAL IS IN SUBSTANTIALLYTHAT CONDITION IN WHICH IT SOLIDIFIED BY DEFORMING SAID CAST METAL ASUBSTANTIAL NUMBER OF TIMES TO CAUSE SAID CAST METAL TO ASSUME APLURALITY OF SUCCESSIVE ALTERNATELY DIFFERENT CROSS-SECTIONS WHICHINCLUDE SEVERAL SUBSTANTIALLY FLATTENED AND ELONGATED CROSS-SECTIONS ANDSEVERAL SUBSTANTIALLY ROUND CROSS-SECTIONS SO AS TO IMPART SUBSTANTIALMOVEMENT TO SAID CAST METAL ALONG A PLU-